The present invention relates to a charging generator system including a protective circuit for vehicular use.
A circuit diagram of such a conventional charging generator system of this type is shown in FIG. 1. In this figure, reference numeral 1 designates three-phase stator coils, 2, a field coil; 3, a rectifier circuit; 4, a first output terminal of the rectifier circuit; 5, a second output terminal of the rectifier circuit; and 6, a charging generator composed of the elements described above. Also in FIG. 1, reference numeral 7 designates a transistor for switching the current in the field coil 2; 8 a transistor which detects the voltage at the second output terminal 5 of the rectifier circuit and in response controllably drives the transistor 7; D.sub.1 and D.sub.2 diodes; R.sub.1, R.sub.2 and R.sub.3 resistors; and 9 a regulator circuit which is composed of the elements described above. Further in FIG. 1, reference numeral 10 designates a charge display lamp; 11, a keyswitch; and 12, a battery.
The operation of the above-described conventional system will now be described.
When the keyswitch 10 is closed, current flows from the battery 12 through the charge display lamp 10, the field coil 2 and the transistor 7, to thus turn on the charge display lamp 10 and excite the field coil 2. Thereafter, when an engine (not shown) is started and the charging generator 6 is driven, power generation is started. As a result, voltages appear at the first and second rectifier output terminals 4 and 5, respectively, and the battery 12 is charged thereby. Thereafter, when the voltages at the terminals of the charge display lamp 10 become substantially equal to each other, the charge display lamp 10 is turned off and the current of the field coil 2 is supplied directly from the second rectifier output terminal 5.
It is generally true that overheating of the three-phase stator coils or fusing of the soldered joints in the rectifier circuit or the regulator will not occur under normal full-load conditions of the charging generator 6 if the ambient temperature of the generator 6 is lower than about 120.degree. C.
However, in the conventional charging generator system, the peripheral temperature thereof may sometimes exceed 140.degree. C. due to a lack of a cooling water or when climbing very steep slopes or an extraordinarily high atmospheric temperature. Under these circumstances, overheating of the coils of the charging generator or fusing of the soldered joints in the rectifier circuit or the regulator may occur, which causes the charging generator to be incapable of power generation.
Accordingly, it is an object of the present invention to provide a charging generator system including a protective circuit in which the above-mentioned difficulties accompanying a conventional charging generator system are eliminated.